1. Field of the Invention
The present invention relates to a method of producing an electrochemical device, and the electrochemical device produced by this method. More particularly, the present invention relates to a method of producing an electrochemical device, which embraces an electrochemical capacitor such as an electric double layer capacitor and a secondary battery such as a lithium ion secondary battery, and to the electrochemical device produced by this method.
2. Related Background Art
The electrochemical capacitors including the electric double layer capacitors, and non-aqueous electrolyte secondary batteries including the lithium ion secondary batteries are electrochemical devices whose size and weight can be readily reduced. For this reason, they are expected as power supplies or backup power supplies for portable equipment (compact electronic instruments) or the like, or as auxiliary power supplies for battery cars or for hybrid cars, and various studies have been conducted for improvement in performance thereof.
An example of such electrochemical devices improved in performance, having been proposed heretofore, is an electric double layer capacitor consisting of a laminate of polarizable electrodes, a separator, and collectors, which is made by placing a thermally fluidizable material (polyethylene, polypropylene, or the like) between each set of collector and polarizable electrode, heating them under pressure, and thereafter cooling them to effect bonding (Japanese Patent. Application Laid-Open No. 2000-252175). Another proposed configuration for this electric double layer capacitor is such that the thermally fluidizable material is placed between the separator and the polarizable electrodes. This electric double layer capacitor is designed in the foregoing configurations to enhance electrically conductive connection between the collectors and the polarizable electrodes and to facilitate assembly of a cell.
Another example of the electrochemical devices improved in performance, having been proposed heretofore, is an electric double layer capacitor having an adhesion structure in which a separator is interposed between a pair of polarizable electrodes and in which the polarizable electrodes and separator are adhered to each other, and a production method thereof.
In the electric double layer capacitor and the production method thereof, the separator is made of nonwoven fabric or porous film containing 10 or more wt % polyolefin-based resin, and the polarizable electrodes and separator are bonded to each other by applying pressure to the pair of polarizable electrodes under a temperature environment not less than a softening point of the polyolefin-based resin (e.g., reference is made to Claims 1 to 3 in Japanese Patent Application Laid-Open No. 2001-250742).
This electric double layer capacitor is constructed in the above configuration whereby the polarizable electrodes and separator are bonded to be integrated with each other, so as to suppress change of internal resistance due to change of pressing force from two sides of the cell, to suppress peeling-off between the polarizable electrodes and the separator, and to realize excellent long-term reliability.